.ui-loader-background {
    width:100%;
    height:100%;
    top:0;
    padding: 0;
    margin: 0;
    background: rgba(0, 0, 0, 0.3);
    display:none;
    position: fixed;
    z-index:100;
}

.ui-loading .ui-loader-background {
    display:block;
}